This invention relates to an electronic timing circuit and, in particular, relates to a circuit useful to indicate the extended, continued operation of a motor vehicle's turn signals which can result from failure of the self-cancelling mechanism of the turn signals.
The electrical turn signals commonly found on motor vehicles are manually engaged, usually by a lever on the steering column, and are automatically disengaged as the steering wheel is rotated to direct the vehicle out of a completed turn. Frequently, the automatic disengagement means fails to function; e.g., the cancelling mechanism fails or the turn is too slight to activate the cancelling mechanism. Some vehicles also lack a cancelling mechanism.
The audio and visual indicators on the instrument panel of the vehicle are designed to be of limited prominance to avoid unnecessary distraction when the turn signals are operative. As a result, a driver is often unaware that the turn signals have not been cancelled, particularly when travelling at high speeds with substantial engine and wind noise in the vehicle. This results in the often observed vehicle travelling down a highway with its turn signals continuously flashing.
A vehicle exhibiting improperly flashing turn signals is an annoyance to other drivers. Cautious drivers attempt to avoid the vehicle and the vehicle then impedes traffic. Other drivers ignore the vehicle and this creates a harzardous situation when the vehicle does turn.
It is, therefore, desirable to provide warning means having a prominent, visual and/or audible, indicating means which is activated when the turn signals have remained operative for an abnormally extended period. Such a warning means should not, however, be activated by extended periods of operation of the turn signals which are caused by delays in turning of the vehicle which are experienced before turning when waiting for a traffic signal or for traffic to clear an intersection. The warning means, preferably, should also be unaffected by the use of other electrical accessories on the vehicle such as an air conditioner, and should be compatible with most automotive electrical systems to permit retrofitting without any revisions to the existing electrical systems.